Manufacture of rayon



3,082,057 MANUFACTURE OF RAYQN Bernard F. Walker, Asheville, N.C., assignor to American This application is a continuation-impart of application Serial No. 61,039, filed June 9, 1960, which in turn is a continuation of application Serial No. 678,766, filed August 19, 1957, now abandoned. This invention relates to the production of shaped articles of regenerated cellulose from viscose and more particularly to the production of specially modified high tenacity viscose rayon yarn and rayon tire cord having physical properties superior to normally modified yarn and cord.

Due to extensive research being conducted by various rayon manufacturers, improvements in the physical properties of rayon are being made constantly. Although viscose rayon y-arn possesses many qualities that make it especially suitable for use in reinforcing rubber articles such as cord tires and the like, there is a continuing need to improve the strength and resistance to flex fatigue of the yarn. In recent years a most significant technological advance in improving the tenacity and flex life of viscose rayon yarns resulted from the discovery that certain chemicals under particular spinning conditions modify and retard the regeneration of cellulose after extrusion.

These chemical additives which improve the physical properties of the yarn have become known in the art as viscose modifiers. Modifiers that are already disclosed in the prior art include, for example, certain aliphatic and aromatic monoamines, quaternary ammonium compounds, and N-substituted dithiocar-bamic acids having specific solubilities (U.S. Patents 2,535,0445, 2,536,014, and 2,696,423).

The mechanisms by which a modifier changes the normal spinning process have not been definitely established, although several theories have been advanced in this connection. However, the modified yarns have characteristics which are readily distinguishable over normal yarn. At first, investigators discovered that cross sections of the filaments produced under the influence of'a modifier show that the filaments have a surface with notably reduced crenulations. At the same time, it was found that a modified yarn has a very different skin and core structure which could be observed by viewing stained cross sections of the yarn under a microscope. A modified yarn, it was seen, has a greater proportion of skin to core, as compared with yarn formed by the conventional methods.

In observing the skin structure of a modified yarn, another visible characteristic was always associated with modified yarns. Dark spots could be seen throughout the cross sectional area of the yarns when cross sections of modified yarns were stained and viewed under a light microscope. Initially, no explanation could be given for these dark spots, which later became known as freckles.

Subsequently, it was discovered by observing longitudinal sections of modified yarns under an electron microscope, that the so-called freckles were in fact tiny voids or cavities in the yarns. Generally, the voids are elliptical in cross section with the long axes thereof paralleling the yarn axis which indicated that the voids are present prior to the stretching of the yarn, because stretching orients and elongates the voids. Accordingly, it was thought that the effectiveness of viscose modifiers was somewhat related to the formation of the voids within the freshly spun yarn in View of the fact that the voids were always present in the known modified yarns.

After the discovery that certain chemicals modify the regeneration of cellulose, research work was directed to- 3,982,951 Patented Mar. 19, 1961 Ward finding other chemicals that would exert a mor desirable effect than the known additives. Along this lin it was found that yarn properties are enhanced in a mo: favorable manner when the viscose is spun in the presenc of ethoxylated amines such as those disclosed in US Patent No. 2,572,217 and quaternary derivatives of suc ethoxylated primary amines.

However, when using these types of ethoxylated amine and their derivatives, foaming problems were encountere when the additive was incorporated during the dissolvin of the xanthate crumbs and additionally, the viscose cor taining the additive was very difficult to deaerate.

Another phenomenon that was observed was that th viscose containing the additive became cloudy sever; hours after the modifier was added to the viscose. A; patently, a reaction occurs between the viscose and th modifier which may be either physical or chemical an which produces objectionable products that may be eithe soluble, giving clear viscose, or insoluble, giving cloud viscose. It seems likely that the by-products of this reac tion are produced at a steady rate commencing as 500 as the viscose and the modifier are mixed. It would als seem probable that the sudden development of cloudines is only incidental and may occur at the time when th concentration of reaction products suddenly reaches th limit of their solubility in the viscose. There are thu two probabilities, either (a) soluble, harmful reactio products present in the viscose from the moment of mi) ing, increasing in concentration with time; and (b) it soluble, harmful reaction products which develop some time after mixing, which apparently induce the form: tion of voids discussed above.

In an effort to overcome these problems, and mor particularly the foaming and deaeration problems, th modifier was injected into the viscose just prior to spit ning the viscose. The aforesaid problems were effective ly overcome but, what was quite unexpected, the physicz properties of the cord made from the yarn were significan' ly improved, especially in regard to strength withot sacrificing resistance to flex fatigue, as will be shown hert inafter. The injection method apparently circumvent the harmful effect of by-products whether soluble or it soluble. The primary benefit of using the injection sy: tem seems to be that the strength of the cord is significan' 1y improved, or in other words, the cording loss is Cit creased.

Heretofore the point at which the modifier was adde to the spinning process was not considered critical as ion as the additive was present when the viscose was extrude into the setting bath. The prior art suggested very gene] ally that the modifier could be added to the setting bat] to the viscose, or in almost any stage in the productio of viscose. The primary considerations in this resper were the stability and solubility of the modifier with se ondary attention given to improvements in the physicz properties of the yarn.

On the contrary, by the present invention it has bee found that the time at which the modifier is added t the viscose spinning system is highly important to produc a modifier yarn which forms superior cords. It has no been discovered that by adding the modifier to the viscos spinning solution shortly before it reaches the SPlIlIlCTv and thereafter spinning the viscose, improved proces ability and improved physical properties of the cord a1 obtained. In addition to avoiding the foaming and deaer: tion problems and improving the strength and resistant to flex fatigue, a brighter yarn is produced by the prese1 invention. Furthermore, the yarn of the present inventic very surprisingly is substantially free from the voids discussed above.

It is' an object of the present invention to provide process for manufacturing high tenacity modified regel :rated cellulose yarn from viscose thatforms cords of mproved physical properties as compared with known nodified yarn cord.

An additional object is to provide a high tenacity, highly atigue-resistant modified cord that is characterized by he substantial absence of voids normally present in modiied yarns.

Other objects and advantages will become apparent rom the following detailed description.

These objects are accomplished by incorporating in the 'iscose a modifier at a time not too remote from the pinning of the viscose into a setting bath. Compounds generally suitable for use in accordance with the present nvention are those additives which, when added to a visose solution in sufficient amounts, retard the subsequent egeneration of the cellulose but during ripening of the 'iscose will normally form a cloudy viscose solution. In .ddition, these compounds may be distinguished by the act that they tend to induce aeration and foaming in the 'iscose.

Among the compounds suitable in the practice of the resent invention are those described in application Serial -10. 609,792, now abandoned, and in said U.S. Patent -10. 2,572,217. These compounds have the general ormula:

(GDHZHOLH R1N+ Z- 1 tz (CuH2nO) H vhere R and R represent preferably an alkyl radical rut may include an aryl or alicyclic radical with R prefrably being an alkyl radical containing six or more arbon atoms and R being an alkyl radical containing me to three carbon atoms; Z represents an anion having ubstantially no surface activity such as hydroxide, halide, ulfate, acetate, etc.; x and y are whole numbers of at east one with the preferred combined value of x and y cing 2 to 50 more, depending on the purpose for which he additiveis used; 11 is also a whole number, possibly me but preferably two or no more than four. These qua- :rnary derivatives of ethoxylated primary amines are nown in the trade as Ethoquads.

The compounds of U.S. Patent No. 2,572,217 are known 1 the trade as Ethomeens and are reaction products of mg chain aliphatic primary amines with ethylene oxide, 1e reaction being represented generally as follows:

(CnH2nO) :11

ENE: (z wonmno RN u ZnO) 11 11 the above formula, R represents an aliphatic chain aving from 8 to 24 carbon atoms therein and preferably rom 12 to 14 carbon atoms. x or y is at least one, nd x plus y is the total number of alkylene oxide chains lhlClZl may be as low as without any definite restriction n the upper limit, although 12 to 18 or about 15 have een found to be quite effective, and n is a small whole umber from 2 to 4, both inclusive.

A preferred method of adding the modifier to the visose is by injecting predetermined amounts, e.'g. 1.0%- .0% of the material based on the weight of the cellulose no a flowing stream of viscose by any suitable type of ijection system, such as that shown in application Serial 10. 655,004, filed April 25, 1957, now Patent No. 329,731, and having common ownership herewith, aoroughly mixing the viscose and modifier and thereafter pinning the mixture in a conventional manner.

The yarn produced by the present invention is par- .cularly characterized by the fact that it is substantially ll skin modified viscose rayon yarn having tenacity and atigue resistance in a cord construction superior to ormally modified yarn and further characterized by a ubstantial absence of freckles when viewed under a light iicroscope and a substantial absence of voids when viewed under an electron microscope. Furthermore, the yarn has a brighter luster than normally modified yarn.

A further understanding of the process and the novel yarn of this invention will be obtained from the following specific examples which are intended to illustrate the present invention, but not to limit the scope thereof.

EXAMPLE I Alkali cellulose prepared from wood pulp was aged in a known manner. This alkali cellulose Was then xanthated with 37.7% carbon disulfide, based on the weight of the cellulose. The xanthate crumbs so produced were dissolved in a solution of sodium hydroxide of a predetermined strength to produce a viscose having 7.5% cellulose and 5.7% sodium hydroxide. During the dissolving process a viscose modified, namely the methyl chloride quaternary derivative of an ethoxylated coconut oil amine having the general formula:

(CHZOHZO) :H

RN+ o1- w izCHzOhH in which formula x plus y=approximately l5 and R is a saturated hydrocarbon radical containing 8l8 carbon atoms, was added in the amount of 2.5% based on the cellulose content. Foaming was noticeable in the dis solving operation; and the viscose could not be efficiently deaerated in the usual vacuum deaerating tanks. It was observed that the viscose became somewhat turbid after about four hours.

The viscose, after being properly filtered and aged, was spun into yarn by extruding it through a spinneret into a primary setting bath containing 4.8% sulfuric acid, 13.7% Na S-O and 4.0% ZnSO The temperature of the bath was maintained at 65 C. Thereafter the yarn was given a high stretch in a second bath having the composition of 4.0% sulfuric acid, 4.0% sodium sulfate, and 0.7% zinc sulfate, said bath being maintained at 93 C. The yarn was aftertreated in a conventional manner.

The conditioned and wet strength values of unslashed singles of the yarn so produced were respectively 411 g/ denier and 305 g./100 denier. Singles given a 10% slashing stretch had a conditioned strength of 445 g./ 100 denier and a wet strength of 321 g./100 denier.

The slashed singles were plied into the tire cord construction seen in Table I wherein physical properties thereof are given.

Table I Cord construction 11.4 x 10 6 12 x 12 12/11 Denier 3, 613 Conditioned strength, lbs 30. 6 Conditioned strength, g./100 den 384 Oven dry strength, lbs 36. 4 Oven dry strength, g./l00 den 457 Firestone fatigue, hrs.

The yarn appeared to be dull and milky when observed on a yarn viewing card. Cross sections of the yarn when stained and viewed under a light microscope showed the ifreckles as described above. By viewing longitudinal sections of the yarn under an electron microscope, it was noted that the yarn had many voids within the yarn.

EXAMPLE II The viscose was extruded into a primary bath having the same composition as in Example -I. The yarn was stretched, passed through a second bath, and aftertreated in the manner also described in Example I.

The conditioned and wet strength values of unslashed singles of the yarn so produced were respectively 395 g./ 100 denier and 310 g./100 denier. Singles given a slashing stretch had a conditioned strength of 460 g./100* denier and a Wet strength of 325 g /100 denier.

The slashed singles were plied into the tire cord construction seen in Table II wherein physical properties thereof are given.

An analysis of the data given in the tables showing a highly significant improvement in the cord strengths of the yarn produced by injecting the additive into the ripened viscose as compared with the yarn produced by incorporating the additive during the dissolving operation.

The yarn produced in the present example had a bright, lustrous appearance when observed on a yarn viewing card. The spinnability of the viscose was improved and the viscose was very clear when extruded. Cross sections of the yarn, when stained and viewed under a light microscope, were practically free of freckles and had a homogeneous skin structure. By viewing longitudinal sections of the yarn under an electron microscope, substantially no voids were noticed within the y The yarn had a high degree of molecular orientation as determined by X-ray diifraction measurement. Although high orientation is characteristic of high tenacity but ordinarily brittle yarn, it was surprising that such properties would be present in the yarn of the instant invention, especially in view of the fact that the present yarn is not brittle but is highly resist-ant to flex fatigue.

While the specific examples of the preferred methods embodying the present invention have been set forth above, it will be understood that many changes and modifications may be made in the methods of procedure with out departing from the spirit of the invention.

What is claimed is:

1. In a method of producing a high tenacity modifier viscose rayon yarn involving the use of a type of modifie which when added to the viscose solution in the re quired amounts will normally induce aeration and foam ing therein, the improvement that comprises injecting 1.0 6.0%, based on the weight of the cellulose in the viscose of a modifier of the class consisting of ethoxy-lated amine and quaternary derivatives thereof, into a flowing strean of normally ripened viscose just prior to spinning, pass ing the mixture into a blending zone, and before an objectionable aeration and foaming can occur in the vis cose solution, directly extruding the same into a coagul-at ing bath to form yarn therefrom.

2. In a method of producing a high tenacity modifier viscose rayon yarn involving the use of a type of modi fier which when added to the viscose solution in the re quired amounts will normally induce aeration and foam ing therein, the improvement that comprises injecting 1.0- 6.0%, based on the Weight of the cellulose in the viscose of an ethoxylated amine into a flowing stream of normally ripened viscose just prior to spinning, passing the mixturi into a blending zone, and before any objectionable aera tion and foaming can occur in the viscose solution, di rectly extruding the same into a coagulating bath to forn yarn therefrom.

3. In a method of producing a high tenacity modifie viscose rayon yarn involving the use of a type of modifie which when added to the viscose solution in the requiret amounts will normally induce aeration and foaming therein, the improvement that comprises injecting 1.0- based on the weight of the cellulose in the vis cose, of a quaternary derivative of an ethoxylated amini into a flowing stream of normally ripened viscose jus prior to spinning, passing the mixture into a blending zone, and before any objectionable aeration and foam ing can occur in the viscose solution, directly extruding the same into a coagulating bath to form yarn there from.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A METHOD OF PRODUCING A HIGH TENCITY MODIFIED VISCOE RAYON YARN INVOLVING THE USE OF A TYPE OF MODIFIER WHICH WHEN ADDED TO THE VISCOSE SOLUTION IN THE REQUIRED AMOUNTS WILL NORMALLY INDUCE AERATION AND FOAMING THEREIN, THE IMPREVEMENT THAT COMPRISES INJECTING 1.06.0%, BASED ON THE WEIGHT OF THE CELLULOSE IN THE VISCOSE. OF A MODIFIER OF THE CLASS CONSISTING OF ETHOXYLATED AMINES AND QUATERNARY DERIVATIVES THEREOF, INTO A FLOWING STREAM OF NORNALLY RIPENED VISCOSE JUST PRIOR TO SPINNING, PASSING THE MIXTURE INTO A BLENDING ZONE, AND BEFORE ANY OBJECTIONABLE AERATION AND FOAMING CAN OCCUR IN THE VISCOSE SOLUTION, DIRCETLY EXTRUDING THE SAME INTO A COAGULATING BOTH BATH TO FORM YARN THEREFROM. 